Cadherins are integral membrane proteins that mediate calcium-dependent cell-cell adhesion. Type I cadherin proteins are composed of a large N-terminal extracellular domain, a single membrane-spanning domain, and a small, highly conserved C-terminal cytoplasmic domain. The extracellular domain consists of five subdomains, each containing a cadherin motif, and appears to determine the specificity of the protein's homophilic cell adhesion activity. Type II (atypical) cadherins are defined based on their lack of a HAV cell adhesion recognition sequence specific to type I  cadherins. Cadherin 8, also known as CDH 8, is a type I I classical cadherin belonging to the cadherin superfamily. As mainly expressed in brain, CDH8 is found in certain nerve cell lines, such as retinoblasts, glioma cells and neuroblasts, and is putatively involved in synaptic adhesion, axon outgrowth and guidance. Human Cadherin 8 is a 799 amino acid single-pass type I  transmembrane protein with a putative 29 aa signal sequence, and a 32 aa propeptide, a 560 aa mature extracellular domain, a 21 aa transmembrane domain and a 157 aa cytoplasmic domain. The human, mouse and rat proteins share approximately 98% homology.